What is short sight?
　　When light entering into our eyes, it will refract via eye lens and form image at retina, and we can see things once the image is transmitted to eye nerve center of cerebra. And the so-called short sight indicates the state that the position of the image forming is in front of the retina.
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short sight has two types:

　　First type: axis short sight caused by the front and back dia. of the eye longer than the normal length. Another type: dioptre short sight caused by too strong diopter. But the pure dioptre short sight is few excluding some special cases, most of short sight is caused by not matching between dioptre and axis length.

　　Additionally, short sight can also devide another two types: one is natural short sight caused by inherit factor; the other is not natural short sight caused by living environment. And almost all natural short sight are axis short sight which occupy 5 percent of all the short sight sufferers and can only use glasses or contact lens to rectify. And 95 percent are caused by living conditions, most of them are formed at the stage of primary school, middle school and senior high school. At the early stage of short sight’s forming, it can resume to normal sight if being cured in time. This is the so-called false short sight.